NASA Photos Show the Drought's Alarming Effect on the Mississippi River

These images show a stretch of the Mississippi River just south of Memphis, Tennessee. The top one was taken by a NASA satellite on August 8, 2012, and the bottom one by a different NASA satellite on August 14, 2011. See how there are huge patches of light tan along the river in the image from 2012? Those are newly exposed sand bars, the result of record low water levels.

This summer's record-setting temperatures (July was literally the hottest month on record) and dry weather conditions have created historic droughts. We can now see how those conditions have affected our waterways. On August 17 of this year, water levels in the Mississippi were 2.4 to 8.3 feet below their normal "river stage" levels.

This has economic effects, as the NASA Earth Observatory blog points out:

The reduced river flow in 2012 has translated into millions of dollars in extra shipping costs, as the loss of just one inch of draft means that a barge can carry 17 tons less than it otherwise would. The result is decreased shipping capacity.

The current conditions are being described as "uncharted territory." There are potential health effects as well. The low river levels are creating a "wedge" of saltwater that's advancing up the river from the Gulf of Mexico and threatening drinking water in the area.